The malfunctioning of protein kinases (PKs) is the hallmark of numerous diseases. A large share of the oncogenes and proto-oncogenes involved in human cancers code for PKs. The enhanced activities of PKs are also implicated in many non-malignant diseases, such as benign prostate hyperplasia, familial adenomatosis, polyposis, neuro-fibromatosis, psoriasis, vascular smooth cell proliferation associated with atherosclerosis, pulmonary fibrosis, arthritis glomerulonephritis and post-surgical stenosis and restenosis. PKs are also implicated in inflammatory conditions and in the multiplication of viruses and parasites. PKs may also play a major role in the pathogenesis and development of neurodegenerative disorders.
For a general reference to PKs malfunctioning or disregulation see, for instance, Current Opinion in Chemical Biology 1999, 3, 459-465.
Phosphatidylinositol 3-kinases (PI3Ks) are a family of lipid and serine/threonine kinases that catalyze the phosphorylation of the membrane lipid phosphatidylinositol (PI) on the 3′-OH of the inositol ring to produce phosphoinositol-3-phosphate (PIP), phosphoinositol-3,4-diphosphate (PIP2) and phosphoinositol-3,4,5-triphosphate (PIP3), which act as recruitment sites for various intracellular signalling proteins, which in turn form signalling complexes to relay extracellular signals to the cytoplasmic face of the plasma membrane. These 3′-phosphoinositide subtypes function as second messengers in intra-cellular signal transduction pathways (see e.g. Trends Biochem. Sci 22 87, 267-72 (1997) by Vanhaesebroeck et al.; Chem. Rev. 101 (8), 2365-80 (2001) by Leslie et al (2001); Annu. Rev. Cell. Dev. Boil. 17, 615-75 (2001) by Katso et al; and Cell. Mol. Life. Sci. 59 (5), 761-79 (2002) by Toker et al).
Multiple PI3K isoforms categorized by their catalytic subunits, their regulation by corresponding regulatory subunits, expression patterns and signalling specific functions (p110α, β, δ, γ) perform this enzymatic reaction (Exp. Cell. Res. 25 (1), 239-54 (1999) by Vanhaesebroeck and Katso et al., 2001, above).
The closely related isoforms p110α and β are ubiquitously expressed, while δ and γ are more specifically expressed in the haematopoietic cell system, smooth muscle cells, myocytes and endothelial cells (see e.g. Trends Biochem. Sci. 22 (7), 267-72 (1997) by Vanhaesebroeck et al). Their expression might also be regulated in an inducible manner depending on the cellular, tissue type and stimuli as well as disease context. Inductibility of protein expression includes synthesis of protein as well as protein stabilization that is in part regulated by association with regulatory subunits.
Eight mammalian PI3Ks have been identified so far, including four class I PI3Ks. Class Ia includes PI3Kα, PI3Kβ and PI3Kδ. All of the class la enzymes are heterodimeric complexes comprising a catalytic subunit (p110α, p110β or p110δ) associated with an SH2 domain containing p85 adapter subunit. Class la PI3Ks are activated through tyrosine kinase signalling and are involved in cell proliferation and survival. PI3Kα and PI3Kβ have also been implicated in tumorigenesis in a variety of human cancers. Thus, pharmacological inhibitors of PI3Kα and PI3Kβ are useful for treating various types of cancer.
PI3Kγ, the only member of the Class Ib PI3Ks, consists of a catalytic subunit p110γ, which is associated with a p110 regulatory subunit. PI3Kγ is regulated by G protein coupled receptors (GPCRs) via association with βγ subunits of heterotrimeric G proteins. PI3Kγ is expressed primarily in hematopoietic cells and cardiomyocytes and is involved in inflammation and mast cell function. Thus, pharmacological inhibitors of PI3Kγ are useful for treating a variety of inflammatory diseases, allergies and cardiovascular diseases.
These observations show that deregulation of phosphoinositol-3-kinase and the upstream and downstream components of this signalling pathway is one of the most common deregulations associated with human cancers and proliferative diseases (see e.g. Parsons et al., Nature 436:792 (2005); Hennessey et al., Nature Rev. Drug Discovery 4: 988-1004 (2005).
The mammalian target of rapamycin (mTOR) also known as FK506 binding protein 12-rapamycin associated protein 1 (FRAP1) is a protein which in humans is encoded by the FRAP1 gene. mTOR is a serine/threonine protein kinase that regulates cell growth, cell proliferation, cell motility, cell survival, protein synthesis, and transcription. The inhibition of mTORs are believed to be useful for treating various diseases/conditions, such as cancer (for example, as described in Easton et al. (2006). “mTOR and cancer therapy”. Oncogene 25 (48): 6436-46).
The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.
International patent applications WO 99/64401 and WO 02/10140 both disclose compounds that may be useful as agonists or antagonists of somatostatin receptors. These documents do not predominantly relate to imidazopyrazines.
International patent applications WO 2007/028051 and WO 2008/156614 disclose inter alia imidazopyrazines that may be useful as kinase inhibitors. International patent application WO 2009/007029 discloses various compounds that may be useful in the treatment of haematological diseases. However, none of these documents predominantly relate to imidazopyrazines that are substituted at the 8-position with a cyclic group.
International patent applications WO 2004/072080 and WO 2004/072081 both disclose various imidazopyrazines, which may be useful as modulators of HSP90 complex or as modulators of a certain protein kinase. International patent application WO 02/060492 also discloses various imidazopyrazines, which may be useful as inhibitors of a certain protein kinase (JAK kinases). However, all of these documents predominantly relate to imidazopyrazines that are unsubstituted at the 2-, 3- and 5-position.
International patent application WO 2004/022562 discloses various imidazopyrazines that may be useful as modulators of kinase activity. However, this document predominantly relates to imidazopyrazines that are substituted at the 8-position with an amino group containing an aromatic ring and/or imidazopyrazines that are unsubstituted at the 2-, 3-, and 4-position.
International patent application WO 02/062800 discloses various compounds for use as antagonists on a corticotropin-releasing-factor receptor. International patent application WO 88/04298 also discloses certain compounds for use as medicaments. However, these documents do not predominantly relate to imidazopyrazines substituted at the 6-position with an aromatic group and/or relate to those imidazopyrazines unsubstituted at the 2-, 3-, and 4-position.